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It is not known why some people develop gallstones and others do not, but they run in families and a genetic association for gallstones has been found.

Gallstones are most common among older adults, women, and amongst certain ethnic groups. In addition, being obese or overweight increases the risk of gallstones.

Known risk factors associated with diet and being overweight can be modified in order to reduce risk of gallstone formation.

The gallbladder is a small, pear-shaped organ located below the liver. Its primary purpose is to store and deposit gall (also called bile), a digestive liquid produced by the liver. After a meal, the gallbladder contracts and sends the bile into the intestine, where it helps with digestion, mainly of fats. When a meal has been digested, the gallbladder relaxes and fills up again with bile from the liver.

Under certain conditions substances found in bile crystallize and accumulate to form one or more gallstones in the gallbladder. Gallstones can vary in size from a grain of sand to a large pebble. The cause of gallstones is not completely known, but scientists believe they form when the bile contains too much cholesterol, too much bilirubin, not enough bile salts, or when the gallbladder does not empty completely or often enough.

Most people with gallstones do not experience any symptoms and may never even know they have them. If gallstones move from the gallbladder and lodge in any of the ducts that carry bile from the liver to the small intestine, they can cause intermittent pain in the upper abdomen area, especially after meals. If a gallstone gets stuck in any of these ducts, and blocks them completely, the result can be a so-called gallbladder attack, with severe and sudden pain in the right upper part of the abdomen or upper back.

If any of the bile ducts remain blocked for a significant period of time, severe damage or infection can occur in the gallbladder, liver, or pancreas. Left untreated, this can be fatal. Warning signs of a serious problem are fever, jaundice, and persistent pain.

About 1 in 5 individuals will develop gallstones, which may require medical intervention, during their life. Gallstones are more common in individuals over the age of 60, women during childbearing age, and amongst certain ethnic groups. In addition, being obese or overweight increases the risk of gallstones. Gallstone formation often runs in families. Thus, the risk is doubled if one has a first-degree relative with gallstones. It is therefore not surprising that a genetic association has been found for this condition.

The deCODEme Complete Scan identifies a variant (rs6756629) in the ABCG5/ABCG8 gene region on chromosome 2 and provides an interpretation of the risk for developing gallstones that is associated with this variant in customers of European descent. Risk information for other ethnicities is currently unavailable.

Risk Factors

It is not known why some people develop gallstones and others do not. However, it is known that several factors can affect the risk of gallstone formation and many people who get gallstones have a combination of the following risk factors:

• Sex: Women are twice as likely as men to develop gallstones, especially during pregnancy. Excess estrogen from pregnancy, hormone replacement therapy, and birth control pills appear to increase cholesterol levels in bile and decrease gallbladder movement, which can lead to gallstones.
• Age: Women can develop gallstones at a young age due to increased risk during pregnancies. In general though, people older than age 60 are more likely to develop gallstones than younger people.
• Ethnicity: Native-Americans and Mexican-Americans have been found to have a genetic predisposition to secrete high levels of cholesterol in bile. In fact, these groups have the highest rate of gallstones in the United States, whereas African Americans of both sexes have the lowest incidence of gallstones.
• Family history: Gallstones often run in families, the risk of developing gallstones is doubled if one has a first-degree relative with the condition.
• Weight: Obesity is a major risk factor for gallstones, especially in women. Studies have also shown that being even moderately overweight increases the risk for developing gallstones.
• Rapid weight loss: As the body metabolizes fat during prolonged fasting and rapid weight loss the liver secretes extra cholesterol into bile, which can lead to gallstones. In addition, the gallbladder does not empty properly during ‘crash-diets’.
• Diet: It is not clear how diet contributes to gallstone formation. However, diets which are high in cholesterol and fat, and low in fiber, may increase the risk of developing gallstones.
• Cholesterol-lowering drugs: Drugs that lower cholesterol levels in the blood actually increase the amount of cholesterol secreted into bile. In turn, the risk of gallstones increases.
• Diabetes: People with diabetes often have high levels of fatty acids called triglycerides. These fatty acids may increase the risk of gallstones.
• Other diseases People with severe liver diseases and some blood disorders, such as sickle cell anemia, can develop gallstones due to a higher concentration of bilirubin in their bile.

Prevention and Treatment

Although there is no certain prevention for gallstones, many of the risk factors that are associated with diet and being overweight can be modified in order to reduce risk of gallstone formation, such as:

• Maintain a healthy weight. If you are overweight, it is an important health goal in general to lose excess weight gradually, but also important in terms of preventing gallstones. Rapid weight loss followed by weight gain may increase risk for gallstones, especially in women.
• Eat regularly and maintain a balanced diet. Research shows that eating regular meals that contain some fat (which causes the gallbladder to empty) can help prevent gallstones. Eat a balanced diet including plenty of whole grains and fiber, and have regular servings of food that contain calcium (found in green, leafy vegetables and milk products). Limit saturated (animal) fat and foods high in cholesterol.
• Exercise regularly. Studies have shown that increased levels of physical exercise may be an important way to reduce the risk of forming gallstones.
• Estrogen medications. Since estrogen appears to increase cholesterol levels in bile and thereby increase risk of gallstones, women who are at increased risk for gallstones should discuss with their doctors the pros and cons of estrogen therapy such as in hormone replacement therapy, and birth control pills.

The so-called “silent-gallstones” (without symptoms) that so many people have without even knowing about them, are likely to remain silent, and no treatment is recommended.

For gallstones with symptoms, there are several treatment approaches available, but surgical removal of the gallbladder (cholecystectomy) remains the most widely used therapy. This is partly because the newer non-surgical treatments are useful in only some gallstone patients, while surgery can be used in virtually all patients. Patients generally do well after surgery and have no difficulty in digesting food, even though the gallbladder’s function is to aid digestion. Surgical options include the standard procedure, called open cholecystectomy, and a newer, less invasive procedure called laparascopic cholecystectomy (keyhole surgery).

More Information

You can find out more about gallstones by talking to your doctor and visiting these websites:

• American Gastroenterological Association
• Mayo Clinic on gallstones
• National Digestive Diseases Clearinghouse
• American College os Surgeons on Cholecystectomy

Scientific references

1. Howard DE, Fromm H. ‘Nonsurgical management of gallstone disease.’ Gastroenterol Clin North Am. 1999 Mar;28(1):133-44.
2. Buch S, et al. ‘A genome-wide association scan identifies the hepatic cholesterol transporter ABCG8 as a susceptibility factor for human gallstone disease.’ Nat Genet. 2007 Aug;39(8):995-9. Epub 2007 Jul 15..
3. Schirmer BD, Winters KL, Edlich RF. ‘Cholelithiasis and cholecystitis.’ J Long Term Eff Med Implants. 2005;15(3):329-38..

This content was last reviewed on February 08, 2010.

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